For the first 15 years of their existence, Pixar was bulletproof. For the past three years, less so. Following the soaring success of 2010’s “Toy Story 3” was going to be difficult regardless, but 2011’s “Cars 2” and 2012’s “Brave” marked the first time in the company’s history that they released back-to-back films that could be considered disappointments (at least from a critical standpoint; they still made just under $1.1 billion in worldwide ticket sales). With the announcement that their next film would be “Monsters University,” a prequel to 2001’s “Monsters Inc.,” people smelled blood in the water. They’ve run out of ideas. They’re not even trying to be the Pixar of “old.” (That last line is an actual complaint from a fellow critic.) And to be fair, “Monsters University” doesn’t tug at the heart strings the way its predecessor did, but at the same time, how could it? Boo was one of the cutest characters in movie history, and there was no organic way of playing that card in a college setting.

So no, “Monsters University” won’t be anyone’s favorite Pixar movie, but it’s still quite enjoyable, funny, beautifully rendered, and it has a great message for kids about not letting anyone tell you what you can or can’t be. It’s no “Up” or “WALL∙E,” but it’s better than Pixar’s last two films combined, and for that alone, we should be thankful.

Mike Wazowski (Billy Crystal) arrives on the campus of Monsters University with stars in his eyes. He has wanted to be a scarer since he was a little boy, and has read every book on the subject. Jimmy Sullivan (John Goodman), on the other hand, is a prodigy, a natural born scarer who takes his gifts for granted. After both are kicked out of scaring school because of their obvious shortcomings (Sulley is lazy, and Mike just isn’t scary enough), Mike makes a bet with the tough-nosed Dean Hardscrabble (a pitch-perfect Helen Mirren), where she will let him back into scaring school if he and his oddball fraternity brothers win the annual Scare Games competition. If he loses, he’s expelled from school. Yep, it’s “Revenge of the Nerds,” with monsters, and John Goodman on the ‘nerd’ side of the battle this time around.

While the overall story may be a familiar one, the focus of the film is on the relationship between Mike and Sulley, and despite the fact that they’re rewriting history – in “Monsters Inc.,” Mike tells Sully, “You’ve been jealous of my good looks since the third grade,” but here, they’re meeting for the first time – the dynamic feels genuine. The undersized kid who studied his ass off, and the entitled boy who never worked a day in his life; they might be age-old character types, but they’re used effectively, and even when the characters are at their worst, it’s hard not to like them both. They might be stubborn, but they’re not mean, even when everyone else around them is. There’s another good lesson for the kids.

It’s fun to watch Crystal and Goodman do slightly different versions of Mike and Sulley. Indeed, Crystal’s work as Mike ranks with his all-time best stuff. Goodman plays younger Sulley with a bit of a Dude (as in Jeff Bridges) vibe, an ‘it’s all good’ looseness that makes Sulley a good foil for the hyper-driven Mike. Mirren’s dean is a rare feat of animation: beautiful, dignified, and absolutely terrifying. Parents, meanwhile, will double over with laughter when one of the Scare Games competitions involves teenagers.

For those familiar with Pixar’s work, though, there is this unshakable feeling that, as fun and well meaning as the story is, it could be better. This is patently unfair, of course – after all, no one tells Paramount that their newest movie sucks because it’s not as good as “The Godfather” – but it is a very real thing that Pixar will have to deal with going forward. “Monsters University” is very good, but it’s also like listening to Let It Be after spending years listening to Revolver. You know they’re capable of something better than this, and it’s hard not to be a little disappointed.

But really, that’s my problem, and the problem of anyone else who expects Pixar to hit every one of their movies out of the park. What people should accept, moviegoers and critics alike, is that Pixar is in a different stage of its development. They resisted the sequel route far longer than their animation peers, but let’s be pragmatic: they’d be fools not to try and expand the reach of some of their best-known brands (and yes, let us not forget that these movies, in the end, are brands), and even during this sequel phase, they’re only doing it every other movie, so they’re still putting out new content. The fact of the matter is Pixar spoiled us for so long that we don’t know how to react now that they’re doing the things that movie studios do to make money. That’s a nice problem to have, really.